One-pot four component reaction of unsymmetrical 1-methylbarbituric acid with BrCN and various aldehydes in the presence of Et 3N and/or pyridine

Abstract

Reaction of 1-methylpyrimidine-(1H,3H,5H)-2,4,6-trione (1-MBA 1) as an unsymmetrical barbituric acid with cyanogen bromide and various aldehydes in the presence of triethylamine and/or pyridine afforded diastereomeric mixtures of new class of heterocyclic stable 5-aryl-1,1′-dimethyl- and 5-aryl-3,1′-dimethyl-1H,1′H-spiro[furo[2,3-d]pyrimidine-6, 5′-pyrimidine]2,2′,4,4′,6′(3H,3′H,5H)-pentaones which are dimeric forms of 1-methyl barbiturate at the range of 0 oC to room temperature. In the reaction of some aldehydes with 1-MBA and BrCN were afforded a mixture of diastereomers. Another two aldehydes such as 4-cyano- and 2-hydroxybenzaldehydes gave exclusively two diastereomers in which binded to the salt of triethylammonium hydrobromide by intermolecular H-bond in ratio of 1:1. 4-Hydroxybenzaldehyde and 2-pyridine-carbaldehyde gave exclusively one diastereomer under the same condition. Aldehydes possessing strong electron-donor were produced exclusively two geometric isomers of Knoevenagel adduct (E- and Z-isomers). The structures of compounds were deduced by 1H NMR, 13C NMR and FT-IR spectroscopy. Mechanism of the formation is discussed.